in which ρ = density, h = height, ω = angular velocity and r = radius.

Figure 3 shows the respective physical force and its dependence on a bigger radius and higher rotational speed. The results of this study indicate that the centrifugal force represents only a little proportion of effective forces. Hence, the centrifugal forces’ impacts on the tested cells are considered to be insignificant.

Cells were subjected to 24 h of fluid flow rotations at a speed level of 200 rpm. The exposed test cells within the new FSS chamber changed their orientation in accordance with the flow direction. Microscopic evaluation was conducted via a random screening at the peripheral site (2.5-cm radial distance) within a predefined area of interest (0.2 cm × 0.2 cm) through cell counting (at least n = 40 cells/region of interest) and morphological cell characterisation. The FSS-triggered effect was demonstrated as cells realigned themselves towards the flow direction, whereby only cells with an aspect ratio greater than 2:1 were included. To assess the alterations taking place inside the cell body, osteoblast cells were treated with a fluorescence stain to visualise actin fibres. In addition, the cells were split into two groups; the first group (n = 5) remained untreated, without any impact of shear stress (Fig. 4) while the cells in the second group (n = 5) underwent a 24-h rotational impact with 8.35 dyn/cm² shear force. All tests and analysis were repeated at least six times. The cells showed a reproducible (n > 6) realignment of the actin cytoskeleton towards the fluid flow direction (Fig. 5), whereas the actin fibres of the untreated group showed random orientations. Findings were termed a trend if more than 50% of all screened cells (n > 21 cells) underwent reorientation.